Viscosities of engine oils (engine oil and transmission oil) have direct effect on engine and transmission friction, which in turn affect engine idle speed, engine torque output, and gear changes. At lower temperatures, viscosities of the engine oils may be inversely proportional (logarithmically) to temperature. For example, at lower temperatures (higher viscosity) an increased throttle opening (engine airflow) and fuel may be required to achieve a given engine idle speed or engine torque output compared to running the same engine at a higher temperature (lower viscosity). Further, engine starts at low ambient temperatures (cold starts) may adversely affect emissions quality.
Various approaches are provided for accelerated heating of engine oil and engine during an engine start. In one example approach, as shown in U.S. Pat. No. 4,499,365, Puziss shows a portable heater for heating an underbody of a vehicle during cold weather conditions. By supplying heat to the underbody by using a radiant energy generator, such as an infrared lamp or an electric resistance element, engine oil pan and/or crankcase may be heated.
However, the inventors herein have recognized potential disadvantages with the above approach. As one example, in a plug-in hybrid vehicle, the engine may not be in operation for a significant portion of a drive cycle. Therefore, excess engine heat may not be available to warm up the engine oil. Therefore, in order to heat the engine oil, the portable heater may have to be used for a prolonged duration. Use of an external heater may increase parasitic loss of battery power, thereby decreasing the electric-only range of the vehicle and increasing fuel consumption.
The inventors herein have recognized that the issues described above may be addressed by an engine method comprising: prior to an engine start, inductively heating engine oil by coupling a magnetic field between a primary coil external to a vehicle and a ferrous oil pan or a ferrous member coupled to the oil pan, and circulating heated engine oil from the oil pan through one or more engine components during the heating. In this way, by inductively heating an engine oil pan using a charging mat, engine oils and the engine may be preemptively warmed up prior to engine operation.
As one example, an inductive charging mat may be used for wirelessly charge a battery of a plug-in hybrid vehicle. When a vehicle is parked on the charging mat, the on-board battery may be inductively charged without having to physically plug in the vehicle. During charging of the battery, a magnetic field may be created between a primary coil external to the vehicle (on the charging mat) and a secondary coil onboard the vehicle. The magnetic field from the primary coil may be further coupled to a ferrous engine oil pan or a ferrous member coupled to the pan. The magnetic field may cause eddy currents to be induced in the ferrous oil pan or a ferrous member coupled to the pan, thus generating heat. Autonomous vehicles may be able to self-align the vehicle body over the charging mat for recharging the battery and/or warming up engine oils prior to a scheduled vehicle operation. Once the engine oil temperature increases to above a threshold temperature, the heated engine oil may be circulated through the engine components to preemptively heat the engine prior to an actual engine start. During circulation through the engine, if the oil temperature reduces to below the threshold temperature, the oil circulation through the engine may be deactivated and the oil may be continued to be heated until the oil temperature increases to the threshold temperature.
In this way, by preemptively warming engine oil and engine via inductive heating, engine friction may be reduced during engine start, thereby improving engine efficiency. By heating the engine prior to an engine start, cold start emissions may be reduced. The technical effect of using a charging mat to inductively heat the engine oil pan is that engine and engine oil pan heating may be accomplished without the requirement of any additional hardware. Therefore, battery charge may not have to be spent for operating an additional heater. By using self-driving capabilities of an autonomous vehicle, engine oil warm up may be carried out prior to a scheduled vehicle start without intervention of an operator. Overall, by effectively warming the engine and engine oil prior to engine operation, range of operation of a plug-in hybrid vehicle, fuel efficiency, and emissions quality may be improved.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.